Using of Modified Trapping Model in Positron-Lifetime Study of Cold-Worked Aluminium

Abstract

Positron-lifetime (PL) and electrical resistivity studies of polycrystalline aluminium deformed by tensile stress at T 77 K were performed. It was found that the conventional trapping model (CTM) fails in interpretation of measured PL spectra due to strongly non-uniform spatial distribution of dislocations in the deformed samples. Therefore, a modified trapping model (MTM) was used in this study. Strongly non-uniform dislocation density was directly taken into account in the development of MTM. Comparison of the results obtained by MTM and CTM is given in the present work. Mean cell size in the deformed samples obtained from MTM analyses of PL spectra are compared with those measured by TEM. 440 J. C Ï i Âz Ïek et al. J. C Ï i Âz Ïek et al.

Early Stages of Precipitation Process in Al-(Mn-)Sc-Zr Alloy Characterized by Positron Annihilation

“…The longer component with the lifetime s 2 = (250 ± 5) ps and intensity I 2 = (73 ± 1) pct represents a contribution of positrons trapped at defects. Since the lifetime s 2 agrees well with that reported for dislocations in Al, [36,37] we can attribute this component to positrons trapped at dislocations created in the as-cast sample most probably due to non-uniform cooling of the cast ingot. Microstructure observations of the as-cast alloy by TEM proved the presence of dislocations ( Figure 2).…”